Study On The Screening Of Bacterial Strain Against Fungus Of High Moisture Corn And Antibacterial Compounds

Corn is the main food crops in China, and it has become very important industrial rawmaterials and feed ingredients. High moisture corn during storage is easy to mildew andquality deterioration. Penicillium expansum, Fusarium graminearum and Aspergillus nigerare the main source of mildew. Antagonistic bacterial strains against three kinds of indicatorbacteria were isolated and screened from traditional fermented products and the droughty soilusing the method of transparent zone. The species of the antagonistic bacteria was identifiedthrough morphological, physiological and biochemical characteristics, Biolog and16S rDNA.The antibacterial activity ingredients were isolated from fermentation broth by usingammonium sulfate precipitation and macro absorption resin and purified further using HPLC.Molecular weight was determined by electro spray ionization mass spectrometry.1H-NMRand13C-NMR were measured by NMR method and the structure of the compound wasdetermined. Finally the separated active compounds were carried out antagonist tests and itssome physicochemical characteristics were determined. It is aimed at providing the basis andreference for corn mildew. The results are as follows:1. An antagonistic bacterial strain A-1against Penicillium expansum, Fusariumgraminearum and Aspergillus niger was isolated and screened from the drought soil ofGansu central habitat. The antagonistic bacterial strain was identified Bacillus subtilis A-1.2. When the best saturation of ammonium sulfate was50%, the best resin was AB-8, thebest eluent was70%ethanol water, the antagonist precipitate was acquired. Thepreliminary separation component was made a full spectrum scan in190nm to1100nmwavelength. The component had maximum absorbance peak at237nm. The three singletcompounds were further purified using HPLC. The results of inhibiting three kinds ofindicator bacteria experiments proved that when the remaining time was8.114min, thesinglet compound had antibacterial activity.3. ESI-MS displayed molecular ion peak as m/s295[M+H]+，317[M+Na]+, so the molecularweight was294.1HNMR and13CNMR of the singlet compound were determined by NMRmethod. Speculated that the compound of formula was C18H18N2O2. The structure of thecompound was Cyclo-(Phe-Phe）.4. The antibacterial spectrum test results of Cyclo-(Phe-Phe）against the tested seven fungiand three bacteria showed that it inhibited obviously Penicillium expansum, Fusariumgraminearum, Aspergillus niger, Aspergillus oryzae, Aspergillus flavus, Escherichia coli,Enterococcus faecalis and Staphyloccocus aureus. Especially for Penicillium expansum andStaphylococcus aureus, its minimum inhibitory concentration was1μg/mL. 5. The part of physical and chemical properties tests of Cyclo-(Phe-Phe）showed that it hadgood stabilities to heat, acid-base, ultraviolet rays and light.